[Nexus 6P Q&A, Help & Troubleshooting] Nathan-K:
Hey rchtk, nice data! How did you acquire it? Especially the internal resistance measurement. Was that calculated?

I ran a series of experiments on my Nexus 6P using ADB dumpsys batteryproperties and ADB dumpsys battery. I plotted my data here. My conclusions were there is a calibration failure in the software, plus some hardware issues. I used Thevenin Equivalent Circuit modeling and noticed an excessive internal resistance may be contributing to this issue. There are also some "meta" interactions (like Doze low-power states, aluminum body design, lack of global real-world testing during design stage, etc.)

However, I am speculating since I cannot falsify this data by confirming my suspicions/measuring it directly.

I also noticed the sensor poll rate crashes when BatterySaver kicked on, potentially ruining the "emergency shutdown" logic you mentioned. (This would be a "software problem".)

(Part A) https://plus.google.com/102612254593917101378/posts/dpUd5Bm8Df5

(Part B) https://plus.google.com/u/0/102612254593917101378/posts/GCLcr4LqTPo

(Shutoff logged live) https://plus.google.com/u/0/102612254593917101378/posts/SjPzsvmQp4y

(Context) https://plus.google.com/u/0/102612254593917101378/posts/aTCSVkBC7ra

Please see this 4d surface graph I generated illustrating the 2 discharge runs:

("no line" dataset = no heatsinking -- mostly "peach" colored since was restricted current by thermal throttling)

("line-connected" dataset = icepack sinking/thermal reservoir -- mostly "red" colored since power was not throttled)

https://plot.ly/~Nathan-K/2/

Temperature (X axis)

Actual capacity (based off coulomb charge counter) (Y axis)

Cell voltage (Z axis)

Current draw (Color intensity = more)

Please note when loaded at a low temperature, the Coulomb counter -> "% level" reading is wildly inaccurate. It gets stuck at 10% for over an hour, despite 1A of load. So there is something noteworthy about that level. Can you identify what that is in the code?

Second, note how close the "heatsunk" dataset lies to the "3.30v" emergency shutoff value discovered in the "live capture" of a shutdown event. So this might be the "magic" cell voltage value you are seeking.

There are other observation buried in here -- including the max current draw allowed when thermal throttling kicks in, and at what temperatures -- but I allow you to come to your own conclusions. (The more eyes the better!) Please ask if you are curious about mine.

All data and methods are described in the post. I use a Wifi AFB connection and some BASH scripts. You need no specialized tooling to run these tests. Perhaps you can replicate? I am not at liberty to run these experiments due to COI from being a Google Top Contributor in Nexus/Pixel devices. I've actually actively avoided investigating in this topic as a TC to try to keep my data "clean". So independent tests like yours are invaluable.

[Citations]

(1) http://batteryuniversity.com/learn/article/rising_internal_resistance

(2) http://www.ibt-power.com/Battery_packs/Li_Ion/Lithium_ion_tech.html

(3) http://www.richtek.com/en/Design Support/Technical Document/AN023

(4) http://cdn.instructables.com/FVG/29GE/HY12L22N/FVG29GEHY12L22N.LARGE.jpg

(5) http://www.che.sc.edu/faculty/popov/drbnp/WebSite/Publications_PDFs/Web33.pdf

NON-HEATSINKED discharge run (no battery saver)

ICE PACK HEATSINKED discharge run (battery saver kicked in at 15% and was turned off, but still damaged sensor data. Note how there are "two" [% Level vs Charge Counter] graphs.)